Environmentally driven regulatory standards for motor gasoline (mogas) sulfur levels will result in the widespread production of 120 ppm S mogas by the year 2004 and 30 ppm by 2006. In many cases, these sulfur levels will be achieved by hydrotreating naphtha produced from Fluid Catalytic Cracking (cat naphtha), which is the largest contributor to sulfur in the mogas pool. As a result, techniques are required that reduce the sulfur in cat naphthas without reducing beneficial properties such as octane.
Conventional fixed bed hydrotreating can reduce the sulfur level of cracked naphthas to very low levels, however, such hydrotreating also results in severe octane loss due to extensive reduction of the olefin content. Selective hydrotreating processes such as SCANfining have recently been developed to avoid massive olefin saturation and octane loss. Unfortunately, in such processes, the liberated H2S reacts with retained olefins forming mercaptan sulfur by reversion. Such processes can be conducted at severities that produce product within sulfur regulations, however, significant octane loss also occurs.
Hence, what is needed in the art is a process which produces sulfur levels within regulatory amounts and which minimizes loss of product octane.